<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Custom BufferGeometry - Dynamic</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js"
  }
}
</script>

<script type="module">
import * as THREE from 'three';

function main() {

	const canvas = document.querySelector( '#c' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	const fov = 75;
	const aspect = 2; // the canvas default
	const near = 0.1;
	const far = 100;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.z = 3;

	const scene = new THREE.Scene();

	function addLight( ...pos ) {

		const color = 0xFFFFFF;
		const intensity = 3;
		const light = new THREE.DirectionalLight( color, intensity );
		light.position.set( ...pos );
		scene.add( light );

	}

	addLight( - 1, 2, 4 );
	addLight( 2, - 2, 3 );

	function makeSpherePositions( segmentsAround, segmentsDown ) {

		const numVertices = segmentsAround * segmentsDown * 6;
		const numComponents = 3;
		const positions = new Float32Array( numVertices * numComponents );
		const indices = [];

		const longHelper = new THREE.Object3D();
		const latHelper = new THREE.Object3D();
		const pointHelper = new THREE.Object3D();
		longHelper.add( latHelper );
		latHelper.add( pointHelper );
		pointHelper.position.z = 1;
		const temp = new THREE.Vector3();

		function getPoint( lat, long ) {

			latHelper.rotation.x = lat;
			longHelper.rotation.y = long;
			longHelper.updateMatrixWorld( true );
			return pointHelper.getWorldPosition( temp ).toArray();

		}

		let posNdx = 0;
		let ndx = 0;
		for ( let down = 0; down < segmentsDown; ++ down ) {

			const v0 = down / segmentsDown;
			const v1 = ( down + 1 ) / segmentsDown;
			const lat0 = ( v0 - 0.5 ) * Math.PI;
			const lat1 = ( v1 - 0.5 ) * Math.PI;

			for ( let across = 0; across < segmentsAround; ++ across ) {

				const u0 = across / segmentsAround;
				const u1 = ( across + 1 ) / segmentsAround;
				const long0 = u0 * Math.PI * 2;
				const long1 = u1 * Math.PI * 2;

				positions.set( getPoint( lat0, long0 ), posNdx ); posNdx += numComponents;
				positions.set( getPoint( lat1, long0 ), posNdx ); posNdx += numComponents;
				positions.set( getPoint( lat0, long1 ), posNdx ); posNdx += numComponents;
				positions.set( getPoint( lat1, long1 ), posNdx ); posNdx += numComponents;

				indices.push(
					ndx, ndx + 1, ndx + 2,
					ndx + 2, ndx + 1, ndx + 3,
				);
				ndx += 4;

			}

		}

		return { positions, indices };

	}

	const segmentsAround = 24;
	const segmentsDown = 16;
	const { positions, indices } = makeSpherePositions( segmentsAround, segmentsDown );

	const normals = positions.slice();

	const geometry = new THREE.BufferGeometry();
	const positionNumComponents = 3;
	const normalNumComponents = 3;

	const positionAttribute = new THREE.BufferAttribute( positions, positionNumComponents );
	positionAttribute.setUsage( THREE.DynamicDrawUsage );
	geometry.setAttribute(
		'position',
		positionAttribute );
	geometry.setAttribute(
		'normal',
		new THREE.BufferAttribute( normals, normalNumComponents ) );
	geometry.setIndex( indices );

	function makeInstance( geometry, color, x ) {

		const material = new THREE.MeshPhongMaterial( {
			color,
			side: THREE.DoubleSide,
			shininess: 100,
		} );

		const cube = new THREE.Mesh( geometry, material );
		scene.add( cube );

		cube.position.x = x;
		return cube;

	}

	const cubes = [
		makeInstance( geometry, 0xFF0000, 0 ),
	];

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	const temp = new THREE.Vector3();

	function render( time ) {

		time *= 0.001;

		if ( resizeRendererToDisplaySize( renderer ) ) {

			const canvas = renderer.domElement;
			camera.aspect = canvas.clientWidth / canvas.clientHeight;
			camera.updateProjectionMatrix();

		}

		for ( let i = 0; i < positions.length; i += 3 ) {

			const quad = ( i / 12 | 0 );
			const ringId = quad / segmentsAround | 0;
			const ringQuadId = quad % segmentsAround;
			const ringU = ringQuadId / segmentsAround;
			const angle = ringU * Math.PI * 2;
			temp.fromArray( normals, i );
			temp.multiplyScalar( THREE.MathUtils.lerp( 1, 1.4, Math.sin( time + ringId + angle ) * .5 + .5 ) );
			temp.toArray( positions, i );

		}

		positionAttribute.needsUpdate = true;

		cubes.forEach( ( cube, ndx ) => {

			const speed = - 0.2 + ndx * .1;
			const rot = time * speed;
			cube.rotation.y = rot;

		} );

		renderer.render( scene, camera );

		requestAnimationFrame( render );

	}

	requestAnimationFrame( render );

}

main();
</script>
</html>
